<template>
  <div class="pagination">
    <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
    <button v-if="startNumandEnd.start>1" @click="$emit('getPageNo',1)" :class="{active:pageNo==1}">1</button>
    <button v-if="startNumandEnd.start>2">···</button>

    <button  v-for="(page,index) in startNumandEnd.end" :key="index" v-if="page>=startNumandEnd.start" :class="{active:pageNo==page}" @click="$emit('getPageNo',page)">{{page}}</button>
    

    <button v-if="startNumandEnd.end<totalPage-1">···</button>
    <button  v-if="startNumandEnd.end<totalPage" :class="{active:pageNo==totalPage}" @click="$emit('getPageNo',totalPage)">{{totalPage}} </button>
    <button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>

    <button style="margin-left: 30px">共 {{total}} 条</button>
  </div>
</template>

<script>
export default {
  name: 'Pagination',
  props:['pageNo','pageSize','total','continues'],
  computed:{
    //计算有多少页
    totalPage(){
      // 向上取整
      return Math.ceil(this.total/this.pageSize)
    },
    // 计算出连续的页码起始数据和结束数据
    startNumandEnd(){
      // 结构数据
      const {pageNo,continues,totalPage}=this
      // 定义起始数据
      let start=0,end=0
      // 连续的是5页但数据不够5页
      if (continues>totalPage) {
        start=1
        end=totalPage
      }else{
        // start=pageNo-(continues-1)/2
        start=pageNo-parseInt(continues/2)
        end=pageNo+parseInt(continues/2)
        // 如果pageNo很小
        if(start<1){
          start=1
          end=continues
        }
        // 或者很大
        if(end>totalPage){
          end=totalPage
          start=totalPage-continues+1
        }
      }
      return {start,end}
    }
  }
}
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
</style>
